curl https://some-url/ | sh

I see this all over the place nowadays, even in communities that, I would think, should be security conscious. How is that safe? What’s stopping the downloaded script from wiping my home directory? If you use this, how can you feel comfortable?

I understand that we have the same problems with the installed application, even if it was downloaded and installed manually. But I feel the bar for making a mistake in a shell script is much lower than in whatever language the main application is written. Don’t we have something better than “sh” for this? Something with less power to do harm?

  • WolfLink@sh.itjust.works
    1·
    32 minutes ago

    It isn’t more dangerous than running a binary downloaded from them by any other means. It isn’t more dangerous than downloaded installer programs common with Windows.

    TBH macOS has had the more secure idea of by default using sandboxes applications downloaded directly without any sort of installer. Linux is starting to head in that direction now with things like Flatpak.

  • Artyom@lemm.ee
    21·
    11 hours ago

    What’s stopping the downloaded script from wiping my home directory?

    What’s stopping any Makefile, build script, or executable from running rm -rf ~? The correct answer is “nothing”. PPAs are similarly open, things are a little safer if you only use your distro’s default package sources, but it’s always possible that a program will want to be able to delete something in your home directory, so it always has permission.

    Containerized apps are the only way around this, where they get their own home directory.

    • easily3667@lemmus.orgEnglish
      2·
      3 hours ago

      Don’t forget your package manager, running someone’s installer as root

      It’s roughly the same state as when windows vista rolled out UAC in 2007 and everything still required admin rights because that’s just how everything worked…but unlike Microsoft, Linux distros never did the thing of splitting off installs into admin vs unprivileged user installers.

  • tatterdemalion@programming.dev
    93·
    12 hours ago

    Back up your data folks. You’re probably more likely to accidentally rm -rf yourself than download a script that will do it.

    • easily3667@lemmus.orgEnglish
      1·
      3 hours ago

      To be fair that’s because Linux funnels you to the safeguard-free terminal where it’s much harder to visualize what’s going on and fewer checks to make sure you’re doing what you mean to be doing. I know it’s been a trend for a long time where software devs think they are immune from mistakes but…they aren’t. And nor is anyone else.

  • thomask@lemmy.sdf.orgEnglish
    132·
    17 hours ago

    The security concerns are often overblown. The bigger problem for me is I don’t know what kind of mess it’s going to make or whether I can undo it. If it’s a .deb or even a tarball to extract in /usr/local then I know how to uninstall.

    I will still use them sometimes but for things I know and understand - e.g. rustup will put things in ~/.rustup and update the PATH in my shell profile and because I know that’s what it does I’m happy to use the automation on a new system.

        • jagged_circle@feddit.nlEnglish
          1·
          2 hours ago

          You’re telling me that you dont verify the signatures of the binaries you download before running them too?!? God help you.

          I download my binaries with apt, which will refuse to install the binary if the signature doesn’t match.

        • easily3667@lemmus.orgEnglish
          1·
          3 hours ago

          By definition nothing

          The point you appear to be making is “everything is insecure so nothing is” and the point others are making is “everything is insecure so everything is”

      • thomask@lemmy.sdf.orgEnglish
        9·
        13 hours ago

        So tell me: if I download and run a bash script over https, or a .deb file over https and then install it, why is the former a “security nightmare” and the latter not?

        • jagged_circle@feddit.nlEnglish
          1·
          2 hours ago

          Both are a security nightmare, if you’re not verifying the signature.

          You should verify the signature of all things you download before running it. Be it a bash script or a .deb file or a .AppImage or to-be-compiled sourcecode.

          Best thing is to just use your Repo’s package manager. Apt will not run anything that isn’t properly signed by a package team members release PGP key.

  • ikidd@lemmy.worldEnglish
    51·
    18 hours ago

    When I modded some subreddits I had an automod rule that would target curl-bash pipes in comments and posts, and remove them. I took a fair bit of heat over that, but I wasn’t backing down.

    I had a lot of respect for Tteck and had a couple discussions with him about that and why I was doing that. I saw that eventually he put a notice up that pretty much said what I did about understanding what a script does, and how the URL you use can be pointed to something else entirely long after the commandline is posted.

      • billwashere@lemmy.worldEnglish
        4·
        19 hours ago

        Yeah I guess if they were being especially nefarious they could supply two different scripts based on user-agent. But I meant what you said anyways… :) I download and then read through the script. I know this is a common thing and people are wary of doing it, but has anyone ever heard of there being something disreputable in one of this scripts? I personally haven’t yet.

        • Possibly linux@lemmy.zipEnglish
          2·
          18 hours ago

          I’ve seen it many times. It usually takes the form of fake websites that are impersonating the real thing. It is easy to manipulate Google results. Also, there have been a few cases where a bad design and a typo result in data loss.

  • knexcar@lemmy.worldEnglish
    3·
    17 hours ago

    What does curl even do? Unstraighten? Seems like any other command I’d blindly paste from an internet thread into a terminal window to try to get something on Linux to work.

    • irelephant [he/him]🍭@lemm.eeEnglish
      2·
      10 hours ago

      curl sends requests, curl lemmy.world would return the html of lemmy.worlds homepage. piping it into bash means that you are fetching a shell script, and running it.

      • easily3667@lemmus.orgEnglish
        1·
        3 hours ago

        I think he knows but is commenting on the pathetic state of security culture on Linux. (“Linux is secure so I can do anything without concerns”)

        • IngeniousRocks (They/She) @lemmy.dbzer0.com
          1·
          2 hours ago

          What URLs is it not a client for? As far as I understand it will pull whatever data is presented by whatever URL. cURL doesn’t really care about protocol being http, you can use it with FTP as well, and I haven’t tested it yet but now that I’m curious I wanna see if it works for SMB

  • zygo_histo_morpheus@programming.dev
    824·
    1 day ago

    You have the option of piping it into a file instead, inspecting that file for yourself and then running it, or running it in some sandboxed environment. Ultimately though, if you are downloading software over the internet you have to place a certain amount of trust in the person your downloading the software from. Even if you’re absolutely sure that the download script doesn’t wipe your home directory, you’re going to have to run the program at some point and it could just as easily wipe your home directory at that point instead.

    • cschreib@programming.devOP
      7·
      1 day ago

      Indeed, looking at the content of the script before running it is what I do if there is no alternative. But some of these scripts are awfully complex, and manually parsing the odd bash stuff is a pain, when all I want to know is : 1) what URL are you downloading stuff from? 2) where are you going to install the stuff?

      As for running the program, I would trust it more than a random deployment script. People usually place more emphasis on testing the former, not so much the latter.

    • rah@feddit.ukEnglish
      32·
      1 day ago

      You have the option of piping it into a file instead, inspecting that file for yourself and then running it, or running it in some sandboxed environment.

      That’s not what projects recommend though. Many recommend piping the output of an HTTP transfer over the public Internet directly into a shell interpreter. Even just

      curl https://... > install.sh; sh install.sh

      would be one step up. The absolute minimum recommendation IMHO should be

      curl https://... > install.sh; less install.sh; sh install.sh

      but this is still problematic.

      Ultimately, installing software is a labourious process which requires care, attention and the informed use of GPG. It shouldn’t be simplified for convenience.

      Also, FYI, the word “option” implies that I’m somehow restricted to a limited set of options in how I can use my GNU/Linux computer which is not the case.

      • gaylord_fartmaster@lemmy.world
        51·
        20 hours ago

        Showing people that are running curl piped to bash the script they are about to run doesn’t really accomplish anything. If they can read bash and want to review the script then they can by just opening the URL, and the people that aren’t doing that don’t care what’s in the script, so why waste their time with it?

        Do you think most users installing software from the AUR are actually reading the pkgbuilds? I’d guess it’s a pretty small percentage that do.

        • rah@feddit.ukEnglish
          11·
          5 hours ago

          Showing people that are running curl piped to bash the script they are about to run doesn’t really accomplish anything. If they can read bash and want to review the script then they can by just opening the URL

          What it accomplishes is providing the instructions (i.e. an easily copy-and-pastable terminal command) for people to do exactly that.

          • gaylord_fartmaster@lemmy.world
            21·
            5 hours ago

            If you can’t review a bash script before running it without having an unnecessarily complex one-liner provided to you to do so, then it doesn’t matter because you aren’t going to be able to adequately review a bash script anyway.

      • zygo_histo_morpheus@programming.dev
        23·
        1 day ago

        I mean if you think that it’s bad for linux culture because you’re teaching newbies the wrong lessons, fair enough.

        My point is that most people can parse that they’re essentially asking you to run some commands at a url, and if you have even a fairly basic grasp of linux it’s easy to do that in whatever way you want. I don’t know if I personally would be any happier if people took the time to lecture me on safety habits, because I can interpret the command for myself. curl https://some-url/ | sh is terse and to the point, and I know not to take it completely literally.

        • rah@feddit.ukEnglish
          41·
          1 day ago

          linux culture

          snigger

          you’re teaching newbies the wrong lessons

          The problem is not that it’s teaching bad lessons, it’s that it’s actually doing bad things.

          most people can parse that they’re essentially asking you to run some commands at a url

          I know not to take it completely literally

          Then it needn’t be written literally.

          I think you’re giving the authors of such installation instructions too much credit. I think they intend people to take it literally. I think this because I’ve argued with many of them.

  • lemmeBe@sh.itjust.works
    252·
    1 day ago

    I think safer approach is to:

    1. Download the script first, review its contents, and then execute.
    2. Ensure the URL uses HTTPS to reduce the risk of man-in-the-middle attacks
    • jagged_circle@feddit.nlEnglish
      3·
      14 hours ago

      Key being reduce. Https doesn’t protect from loads of attacks. Best to verify the sig.

      If its not signed, open a bug report

    • Steve Dice@sh.itjust.worksEnglish
      14·
      1 day ago

      If you’ve downloaded and audited the script, there’s no reason to pipe it from curl to sh, just run it. No https necessary.

      • isaaclw@lemmy.world
        32·
        19 hours ago

        The https is to cover the factthat you might have missed something.

        I guess I download and skim out of principle, but they might have hidden something in there.

        • Steve Dice@sh.itjust.worksEnglish
          3·
          18 hours ago

          Wat. All https does is encrypt the connection when downloading. If you’ve already downloaded the file to audit it, then it’s in your drive, no need to use curl to download it again and then pipe it to sh. Just click the thing.

  • serenissi@lemmy.world
    183·
    1 day ago

    Unpopular opinion, these are handy for quickly installing in a new vm or container (usually throwaway) where one don’t have to think much unless the script breaks. People don’t install thing on host or production multiple times, so anything installed there is usually vetted and most of the times from trusted sources like distro repos.

    For normal threat model, it is not much different from downloading compiled binary from somewhere other than well trusted repos. Windows software ecosystem is famously infamous for exactly the same but it sticks around still.